In addition to desirable hydrocarbons in the form of oil and/or gas, a hydrocarbon well oftentimes produces undesirable water. After having been produced for some time, such wells frequently produce large amounts of water to the surface along with hydrocarbons. This is particularly applicable at later stages of the production lifetime of such a well, the stages at which water may amount to as much as 98% by volume of the outflow, and at which the water may include both formation water and potential injection water. Handling of produced water involves substantial costs associated with, among other things, lifting, separation and disposal thereof.
In a well outflow containing such water, the water will occupy a volume that otherwise could have been filled with desirable hydrocarbons. Thereby the hydrocarbon outflow rate from the production well will be reduced relative to a corresponding well outflow containing mainly hydrocarbons. Insofar as the specific gravity of water normally is larger than that of hydrocarbons, such water will also increase the specific gravity of well outflow relative to that of a mainly hydrocarbon-containing outflow. In general, a water-containing well outflow will therefore require more pressure energy than that of hydrocarbon-containing outflow to be lifted to the surface, which implies that less pressure energy remains to drive produced fluids out of the well. Thereby both the combined outflow rate and the hydrocarbon outflow rate from the well are reduced, and large amounts of water in the outflow eventually may cause the production flow to stop completely, thereby making it difficult to start the well after a production shut-down. A water-containing production flow also increases the probability of oil/water emulsions forming in the outflow. Oftentimes, such emulsions are problematic during separation in surface-based separation equipment in terms of reducing, among other things, the separation efficiency of the separation equipment. Moreover, a large content of water in the outflow may require the production rate to be reduced due to capacity limitations of such surface-based separation equipment.
Furthermore, produced water cause some environmental problems and challenges. In general, water separated from hydrocarbons at the surface must be purified before being disposed or dumped at the surface. This type of water purification normally involves undesirable use of chemicals as well as associated costs and environmental problems.
In light of the aforementioned problems and challenges associated with water undesirably produced to the surface, it would be of great significance if produced water could be separated and removed down in the production well, and without having to be brought to the surface for further processing. Such a technical solution would provide great environmental, process technological and economic advantages.